With the development of technology, wearable electronic devices (e.g., smart watches and smart bands) that are communicatively connected to an electronic device (e.g., a smart phone) through short-range wireless communication have appeared in the market. Such wearable electronic devices provide new experiences to users through various kinds of notification services, call services, email/SNS confirmation functions, and exercise measurement services. The wearable electronic devices are of varying types, some of which can be detachably coupled to a part of a human body or clothing, such as head-mounted displays, smart glasses, smart watches or wristbands, contact lenses type device, ring-shaped devices, shoe-type devices, clothing-type devices, and glove-type devices.
As the resolution and the operational speed of electronic device displays are increased and the performance of a graphic processing devices are improved, a virtual reality display, which was previously operated only on a large-scale appliances, has recently become increasingly miniaturized and light-weight. For example, a user of an electronic device can view 3-Dimensional (3D) images, which could previously be viewed only on a 3D television, through a small-sized virtual reality display device, and can also experience 360-degree panoramic images, which had low utilization in the past, through the virtual reality display device. The user of the electronic device can thus feel a sense of reality and virtual presence, which is unavailable through existing PC monitors or smart phone, through Head-Mounted Display (HMD) equipment capable of sensing movements of a head through an acceleration sensor of the HMD equipment.